3. Architecture (the collective noun) is the real set of artifacts that the Architecture-Specification describes. In other words, this is the observable Architecture in a defined System. The specification may be describing desired future states of that System. Some parts of that specification might never be implemented in practice, since it serves as a vehicle to discuss architectural possibilities and options.

4. Architecture Description: This can be broader than a specification, and include models, prototypes, and real Systems to aid in describing a real or projected Architecture.
(Note: the term “Architecture Description” is an IEEE term, it is NOT used in the Planguage sense of a “Description” Parameter: it should really be equated to the Planguage-Term, “Definition.”)